1. Field of the Invention
The present invention relates to a hole transporting polymer, a method of producing the same, and an organic electroluminescence device (hereinafter referred to as an xe2x80x9corganic EL devicexe2x80x9d, sometimes) using the hole transporting polymer.
2. Description of the Related Art
An inorganic electroluminescence device (hereinafter referred to as an xe2x80x9cinorganic EL devicexe2x80x9d, sometimes) using an inorganic fluorescent substance has hitherto been used for a flat light source as backlight, a display device such as flat panel display or the like, but a high-voltage alternating current was required for driving the devices.
Tang et al. have recently fabricated an organic EL device having a two-layer structure, comprising a laminate of a light emitting layer of an organic fluorescent dyes and a layer of an organic charge transporting compound generally used in a photosensitive layer for electrophotography (U.S. Pat. No. 4,539,507). Since the organic EL device has a feature that emission of various colors can be easily obtained, in addition to low-voltage driving and high luminance, in comparison with the inorganic EL device, various attempts have been made and reported regarding the development and improvement of the device structure, organic fluorescent dyes and organic charge transporting compounds, etc [Jpn. J. Appl. Phys. Vol. 27, page L269 (1988); and J. Appl. Phys., Vol. 65, page 3610 (1989)]
As the hole transporting material, for example, various compounds such as oxadiazole derivatives, oxazol derivatives, hydrazone derivatives, triarylpyrazoline derivatives, arylamine derivatives, stilbene derivatives and the like have been reported.
In case of using only a low molecular weight hole transporting material in the organic EL device, the mechanical strength and heat resistance of the hole transporting layer were insufficient. As the method of forming a hole transporting layer, deposition under vacuum is generally used but has a problem of high production cost. To the contrary, there have been reported a lot of examples using the hole transporting polymer, such as organic EL device using a polystyrene derivatives having an aromatic amine group on the side chain (JP-A-8-259935), organic EL device using a polyester having an aromatic amine group(JP-A-8-259880) and the like, for the purpose of improving the durability and film-forming property. However, these organic EL devices are not necessarily satisfactory in view of the stability on driving.
On the other hand, in a photosensitive layer for electrophotography using the hole transporting material, like the organic EL device, the addition of a polysiloxane is performed for the purpose of preventing deterioration caused by corona discharge. Furthermore, there has been reported a hole transporting polysiloxane obtained by mixing a silicon hole transporting material with a curable polysiloxane and curing the mixture for the purpose of imparting the hole transporting property to the polysiloxane (JP-A-9-124943).
As an example of using a hole transporting polysiloxane in an organic EL, an organic EL device obtained by mixing a polysiloxane having a carbazole group on the side chain with a light emitting polymer has been proposed (WO 9501871).
An object of the present invention is to provide a hole transporting polymer having excellent hole transporting property, excellent durability and excellent film-forming property, and a method of producing the same, and an organic EL device having excellent light emitting characteristics, using the hole transporting polymer.
The present inventors have intensively studied to solve these problems, and found that a specific novel hole transporting polymer has excellent hole transporting property, excellent durability and excellent film-forming property, and that an organic EL device prepared by using the hole transporting polymer has excellent light emitting characteristics. Thus, the present invention has been accomplished.
That is, the present invention relates to [1] a hole transporting polymer comprising a repeating structural unit represented by the following general formula (1), and having a polystyrene-reduced number-average molecular weight of from 103 to 107: 
wherein R1 represents an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; Ar1 represents an arylene group having 6 to 30 carbon atoms, or an arylene ethenylene group represented by the following general formula (2); Ar2 and Ar3 independently represent an aryl group having 6 to 30 carbon atoms, an aromatic amine group represented by the following general formula (3), or an arylene ethenylene group represented by the following general formula (4); and a ring may be formed between Ar1 and Ar2, or Ar1 and Ar3, or Ar2 and Ar3: 
wherein Ar4 and Ar5 independently represent an arylene group having 6 to 30 carbon atoms; R2 and R3 independently represent hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms: 
wherein Ar6 represents an arylene group having 6 to 30 carbon atoms; R4 and R5 independently represent an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; and a ring may be formed between Ar6 and R4, or Ar6 and R5, or R4 and R5: 
wherein Ar7 represents an arylene group having 6 to 30 carbon atoms; R6 and R7 independently represent hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; Ar8 represents an aryl group having 6 to 30 carbon atoms.
The present invention also relates to [2] a hole transporting polymer comprising a repeating structural unit represented by the following general formula (5), and having a polystyrene-reduced number-average molecular weight of from 103 to 107: 
wherein Ar9 and Ar11 independently represent an arylene group having 6 to 30 carbon atoms, an aromatic amine group represented by the following general formula (6) or an arylene ethenylene group represented by the following general formula (7); Ar10 represents an aryl group having 6 to 30 carbon atoms, an aromatic amine group represented by the following general formula (8) or an arylene ethenylene group represented by the following general formula (9); a ring may be formed between Ar9 and Ar10, or Ar9 and Ar11, or Ar10 and Ar11; and R8, R9, R10 and R11 independently represent hydroxy group, an alkyl or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, a group represented by the following general formula (10) or (12), or divalent oxygen atom which may be bonded to an intramolecular silicon atom by crosslinking or to a silicon atom in the molecule vicinally sited by crosslinking: 
wherein Ar12 and Ar13 independently represent an arylene group having 6 to 30 carbon atoms; R12 represents an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; and a ring may be formed between Ar12 and Ar13, or Ar12 and R12, or Ar13 and R12: 
wherein Ar14 and Ar15 independently represent an arylene group having 6 to 30 carbon atoms; and R13 and R14 independently represent hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms: 
wherein Ar16 represents an arylene group having 6 to 30 carbon atoms; R15 and R16 independently represent an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; and a ring may be formed between Ar16 and R51, or Ar16 and R16, or R15 and R16): 
wherein Ar17 represents an arylene group having 6 to 30 carbon atoms; R17 and R18 independently represent hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; and Ar18 represents an aryl group having 6 to 30 carbon atoms: 
wherein Ar19 and Ar21 independently represent an arylene group having 6 to 30 carbon atoms, an aromatic amine group represented by the above general formula (6) or an arylene ethenylene group represented by the above general formula (7); Ar20 represent an aryl group having 6 to 30 carbon atoms, an aromatic amine group represented by the above general formula (8) or an arylene ethenylene group represented by the above general formula (9); and a ring may be formed between Ar19 and Ar20, or Ar19 and Ar21, or Ar20 and Ar21; R19 and R20 independently represent hydroxy group, an alkyl or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, or divalent oxygen atom which may be bonded to an intramolecular silicon atom by crosslinking or to a silicon atom in the molecule vicinally sited by crosslinking; R21 represents hydrogen atom or a group represented by the following general formula (11): 
wherein R22, R23 and R24 independently represent hydroxy group, an alkyl group or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms: 
wherein R25, R26 and R27 independently represent an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, or an arylene ethenylene group represented by the above general formula (9) or an aromatic amine group represented by the following general formula (13): 
wherein Ar22 represents an arylene group having 6 to 30 carbon atoms, an aromatic amine group represented by the above general formula (6) or an arylene ethenylene group represented by the above general formula (7); Ar23 and Ar24 independently represent an aryl group having 6 to 30 carbon atoms, an aromatic amine group represented by the above general formula (8) or an arylene ethenylene group represented by the above general formula (9).
The present invention also relates to [3] the hole transporting polymer according to [2], wherein the compound group represented by the above general formula (12) is in an amount of from 10% by mole to 150% by mole based on the total silicon atoms belonging to said hole transporting polymer except silicon atoms contained in said compound group, and the content of the hydroxyl group is less than 10% by mole based on the total silicon atoms belonging to said hole transporting polymer except silicon atoms contained in said compound group.
The present invention also relates to [4] a method of producing a hole transporting polymer of [1], wherein at least one silane compound represented by the following general formula (14) is hydrolyzed and condensed: 
wherein X represents a halogen atom or an alkoxy group having 1 to 20 carbon atoms; R1, Ar1, Ar2 and Ar3 are as defined in [1]; and a ring may be formed between Ar1 and Ar2, or Ar1 and Ar3, or Ar2 and Ar3.
The present invention also relates to [5] the method of producing a hole transporting polymer of [2], wherein at least one silane compound represented by the following general formula (15), or a mixture of at least one silane compound represented by the following general formula (15) and at least one silane compound represented by the following general formula (16) is hydrolyzed and condensed. 
wherein R30, R31, R32 and R33 independently represent a halogen atom, an alkyl group or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; R28 and R29 independently represent hydroxy group or an alkoxy group having 1 to 20 carbon atoms; Ar25 and Ar27 are the same with Ar9 as defined in the general formula (5) of [2] or Ar19 as defined in the general formula (10) of [2]; Ar26 is the same with Ar10 as defined in the general formula (5) of [2]; and a ring may be formed between Ar25 and Ar26, or Ar25 and Ar27, or Ar26 and Ar27: 
wherein R35 and R36 independently represent a halogen atom, an alkyl group or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; R34 represents a halogen atom, an alkoxy group having 1 to 20 carbon atoms; Ar28 represents an arylene group having 6 to 30 carbon atoms or an arylene ethenylene group represented by the following general formula (17); Ar29 and Ar30 independently represent an aryl group having 6 to 30 carbon atoms, an aromatic amine group represented by the following general formula (18) or an arylene ethenylene group represented by the following general formula (19); and a ring may be formed between Ar28 and Ar29, or Ar28 and Ar30, or Ar29 and Ar30: 
wherein Ar31 and Ar32 independently represent an arylene group having 6 to 30 carbon atoms; R37 and R38 independently represent hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms: 
wherein Ar33 represents an arylene group having 6 to 30 carbon atoms; R39 and R40 independently represent an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; and a ring may be formed between Ar33 and R39, or Ar33 and R40, or R39 and R40: 
wherein Ar34 represents an arylene group having 6 to 30 carbon atoms; R41 and R42 independently represent hydrogen atom, an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms; and Ar35 represents an aryl group having 6 to 30 carbon atoms.
The present invention also relates to [6] the method of producing a hole transporting polymer of [2] or [3], wherein the hole transporting polymer obtained by [5] is reacted with the compound represented by the following general formula (20), 
wherein X represents a halogen atom or an alkoxy group having 1 to 20 carbon atoms; R25, R26, and R27 are as defined in the general formula (12).
The present invention also relates to [7] an organic electroluminescence device comprising a pair of electrodes of an anode and a cathode, at least one of which is transparent or semitransparent, and at least one layer of an organic material formed between the electrodes, wherein the organic material layer contains the hole transporting polymer described in any one of [1] to [3].
The present invention also relates to [8] an organic electroluminescence device comprising a pair of electrodes of an anode and a cathode, at least one of which is transparent or semitransparent, and a light emitting layer formed between the electrodes, wherein the light emitting layer contains the hole transporting polymer described in any one of [1] to [3].
The present invention also relates to [9] an organic electroluminescence device comprising a pair of electrodes of an anode and a cathode, at least one of which is transparent or semitransparent, and a light emitting layer formed between the electrodes, wherein a hole transporting layer containing the hole transporting polymer described in any one of [1] to [3] is provided adjacent to the light emitting layer between the anode and the light emitting layer.
The present invention also relates to [10] the organic electroluminescence device according to [8] or [9], wherein an electron transporting layer containing an electron transporting compound is provided adjacent to the light emitting layer between the anode and the light emitting layer.
The present invention also relates to [11] the organic electroluminescence device according to any one of [8] to [10], wherein the light emitting layer contains a light emitting polymer, which contains a repeating structural unit represented by the following general formula (21) in the proportion of 50% by mol or more based on the total repeating structural units and has a polystyrene-reduced number-average molecular weight of 103 to 107,
xe2x80x94Arxe2x80x94CRxe2x95x90CRxe2x80x2xe2x80x83xe2x80x83(21)
wherein Ar represents an arylene group or heterocylic compound group having 4 to 20 carbon atoms, which take part in a conjugated bond; and R and Rxe2x80x2 independently represent a group selected from the group consisting of hydrogen atom, alkyl group having 1 to 20 carbon atoms, aryl group having 6 to 20 carbon atoms, heterocyclic compound having 4 to 20 carbon atoms and cyano group.
The first hole transporting polymer of the present invention is a hole transporting polymer containing a repeating structural unit represented by the above general formula (1), and having a polystyrene-reduced number-average molecular weight of from 103 to 107. In view of the film forming property, the polystyrene-reduced number-average molecular weight is preferably from 103 to 106.
In the general formula (1), R1 is a straight-chain or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, preferably a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 22 carbon atoms, and more preferably a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of R1 include alkyl group such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group or the like; cycloalkyl group such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group or the like; aryl group such as phenyl group, naphthyl group, anthryl group, biphenyl group or the like, which may be substituted with methyl group, ethyl group, propyl group; and aralkyl group such as benzyl group, phenethyl group and the like, which may be substituted with methyl group, ethyl group, propyl group.
In the general formula (1), the arylene group for Ar1 is an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene, naphthylene or anthrylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of the arylene group for Ar, include phenylene group, naphthylene group, anthrylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In addition, Ar1 in the general formula (1) may be an arylene ethenylene group represented by the above general formula (2). In the general formula (2), Ar4 and Ar5 are independently an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of Ar4 and Ar5 independently include phenylene group, naphthylene group, anthrylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (2), R2 and R3 are independently hydrogen atom, a straight-chain or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, preferably hydrogen atom, a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 22 carbon atoms, and more preferably hydrogen atom, a straight-chain or branched alkyl group having 1 to 6 carbon atoms, or a phenylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of R2 and R3 independently include hydrogen atom, methyl group, ethyl group, propyl group, or a phenyl group which may be substituted with methyl group, ethyl group, propyl group.
In the general formula (1), the aryl group for Ar2 and Ar3 are independently an aryl group having 6 to 30 carbon atoms, preferably an aryl group having 6 to 20 carbon atoms, and more preferably a phenyl or naphthyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of the aryl group for Ar2 and Ar3 independently include phenyl group, naphthyl group, anthryl group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In addition, Ar2 and Ar3 in the general formula (1) may be independently an aromatic amine group represented by the general formula (3). In the general formula (3), Ar6 is an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene or biphenylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of Ar6 include phenylene group, naphthylene group, anthrylene group, biphenylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (3), R4 and R5 are independently a straight-chain or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, preferably a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 22 carbon atoms, and more preferably a phenyl or naphthyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of R4 and R5 independently include phenyl group, naphthyl group, anthryl group, biphenyl group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (3), a ring may be formed between Ar6 and R4, Ar6 and R5, or R4 and R5.
In addition, Ar2 and Ar3 in the general formula (1) may be independently an arylene ethenylene group represented by the general formula (4). In the general formula (4), Ar7 is an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of Ar7 include phenylene group, naphthylene group, anthrylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (4), Ar8 is an aryl group having 6 to 30 carbon atoms, preferably an aryl group having 6 to 20 carbon atoms, and more preferably a phenyl group which may be substituted with a straight-chain or branched alkyl group having I to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of Ar8 include phenyl group, naphthyl group, anthryl group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (4), R6 a nd R7 are independently hydrogen atom, a straight-chain or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, preferably hydrogen atom, a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 22 carbon atoms, and more preferably hydrogen atom, a straight-chain or branched alkyl group having 1 to 6 carbon atoms, or a phenyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of R6 and R7 independently include hydrogen atom, methyl group, ethyl group, propyl group, or phenyl group which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (1), a ring may be formed between Ar1 and Ar2, Ar, and Ar3, or Ar2 and Ar3.
The first hole transporting polymer may be a copolymer as long as it comprises a repeating structural unit represented by the general formula (1). Examples of other copolymerisable repeating structural unit include a repeating structural unit represented by the following general formula (22). Examples of the copolymer include copolymers containing the repeating structural unit represented by the general formula (1) and at least one kind of repeating structural unit represented by the following general formula (22). The composition of the copolymer is not specifically limited as long as the properties of the hole transporting polymer are not deteriorated. The proportion of the repeating structural unit represented by the general formula (1) based on the total of the repeating units is usually 20-100% by mole and preferably 50-100% by mole. 
wherein Rxe2x80x3s represent an alkyl or aryl group having 1 to 12 carbon atoms, which may be the same or different.
The second hole transporting polymer of the present invention is a hole transporting polymer containing a repeating structural unit represented by the above general formula (5), and having a polystyrene-reduced number-average molecular weight of from 103to 107. In view of the film forming property, the polystyrene-reduced number-average molecular weight is preferably from 103 to 106.
The second hole transporting polymer may be a copolymer which contains a repeating structural unit other than the repeating unit represented by the general formula (5) as long as the properties of the hole transporting polymer are not deteriorated. Examples of other copolymerisable repeating structural unit include a repeating structural unit represented by the above general formula (22). The proportion of the repeating structural unit represented by the general formula (5) based on the total of the repeating units is usually 20-100% by mole and preferably 50-100% by mole.
In the general formula (5), R8, R9, R10 or R11 is independently hydroxy group, a straight-chain or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, a group represented by the general formula (10), a group represented by the general formula (12), or divalent oxygen atom which may be bonded to an intramolecular silicon atom by crosslinking or to a silicon atom in the molecule vicinally sited by crosslinking, preferably hydroxy group, a straight-chain or branched alkyl or alkoxy group having 1 to 10 carbon atoms or a cycloalkyl group having 3 to 10 carbon atoms, a group represented by the general formula (10), a group represented by the general formula (12), or divalent oxygen atom which may be bonded to an intramolecular silicon atom by crosslinking or to a silicon atom in the molecule vicinally sited by crosslinking, and more preferably hydroxy group or a straight-chain or branched alkyl or alkoxy group having 1 to 6 carbon atoms, a group represented by the general formula (10), a group represented by the general formula (12), or divalent oxygen atom which may be bonded to an intramolecular silicon atom by crosslinking or to a silicon atom in the molecule vicinally sited by crosslinking.
Specific examples of R8, R9, R10 or R11 independently include hydroxy group; an alkyl group such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, or the like; alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group or the like; cycloalkyl group such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexl group or the like; aryl group such as phenyl group, naphthyl group, anthryl group, biphenyl group or the like, which may be substitute with methyl group, ethyl group or propyl group; and aralkyl group such as benzyl group, phenethyl group or the like, which may be substitute with methyl group, ethyl group or propyl group.
The divalent oxygen atom which may be bonded to an intramolecular silicon atom by crosslinking or to a silicon atom in the molecule vicinally sited by crosslinking specifically means the oxygen atom sandwiched by two silicon atom when siloxane bond is produced by crosslinking.
In the general formula (5), the arylene group for Ar9 and Ar1 is independently an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene or naphthylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of the arylene group for Ar9 and Ar11 independently include phenylene group, naphthylene group, anthrylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In addition, Ar9 and Ar11 in the general formula (5) may be an aromatic amine group represented by the general formula (6). In the general formula (6), Ar12 and Ar13 are independently an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene or biphenylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of Ar12 and Ar13 independently include phenylene group, naphthylene group, anthrylene group, biphenylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (6), R12 is a straight-chain or branched alkyl group having 1 to 2 0 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, preferably a straight-chain or branched alkyl group having 1 to 10 carbon atoms , a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 22 carbon atoms, and more preferably a phenyl or naphthyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of R12 include phenyl group, naphthyl group, anthryl group, biphenyl group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (6), a ring may be formed between Ar12 and Ar13, Ar12 and R12, or Ar13 and R12.
In addition, Ar9 and Ar11 in the general formula (5) may be independently an arylene ethenylene group represented by the general formula (7). In the general formula (7), Ar14 and Ar15 are independently an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of Ar14 and Ar15 independently include phenylene group, naphthylene group, anthrylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (7), R13 and R14 are independently hydrogen atom, a straight-chain or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, preferably hydrogen atom, a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 22 carbon atoms, and more preferably hydrogen atom, a straight-chain or branched alkyl group having 1 to 6 carbon atoms, or a phenyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of R13 and R14 independently include hydrogen atom, methyl group, ethyl group, propyl group, or phenyl group which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (5), the aryl group for Ar10 is an aryl group having 6 to 30 carbon atoms, preferably an aryl group having 6 to 20 carbon atoms, and more preferably a phenyl or naphthyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of the aryl group for Ar10 include phenyl group, naphthyl group, anthryl group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In addition, Ar10 in the general formula (5) may be an aromatic amine group represented by the general formula (8). In the general formula (8), Ar16 is an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene or biphenylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of Ar16 include phenylene group, naphthylene group, anthrylene group, biphenylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (8), R15 and R16 are independently a straight-chain or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, preferably a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 22 carbon atoms, and more preferably a phenyl or naphthyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of R15 and R16 independently include phenyl group, naphthyl group, anthryl group, biphenyl group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (8), a ring may be formed between Ar16 and R15, Ar16 and R16, or R15 and R16.
In addition, Ar10 in the general formula (5) may be an arylene ethenylene group represented by the general formula (9). Ar17 in the general formula (9) is an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of Ar17 include phenylene group, naphthylene group, anthrylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (9), Ar18 is an aryl group having 6 to 30 carbon atoms, preferably an aryl group having 6 to 20 carbon atoms, and more preferably a phenyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of Ar18 include phenyl group, naphthyl group, anthryl group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (9), R17 and R18 are independently hydrogen atom, a straight-chain or branched alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, preferably hydrogen atom, a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 20 carbon atoms or an aralkyl group having 7 to 22 carbon atoms, and more preferably hydrogen atom, a straight-chain or branched alkyl group having 1 to 6 carbon atoms, or a phenyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of R17 and R18 independently include hydrogen atom, methyl group, ethyl group, propyl group, or phenyl group which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (5), a ring may be formed between Ar9 and Ar10, Ar9 and Ar11, or Ar10 and Ar11.
In the general formula (10), R19 and R20 are independently hydroxy group, a straight-chain or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, or divalent oxygen atom which may be bonded to an intramolecular silicon atom by crosslinking or to a silicon atom in the molecule vicinally sited by crosslinking, preferably, hydroxy group, a straight-chain or branched alkyl or alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms or divalent oxygen atom which may be bonded to an intramolecular silicon atom by crosslinking or to a silicon atom in the molecule vicinally sited by crosslinking, and more preferably, hydroxy group, a straight-chain or branched alkyl or alkoxy group having 1 to 6 carbon atoms or divalent oxygen atom which may be bonded to an intramolecular silicon atom by crosslinking or to a silicon atom in the molecule vicinally sited by crosslinking.
Specific examples of R19 and R20 independently include hydroxy group; alkyl group such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, or the like; alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group or the like; cycloalkyl group such as cycloheptyl group, cyclobutyl group, cyclopentyl group, cyclohexl group or the like; aryl group such as phenyl group, naphthyl group, anthryl group, biphenyl group or the like, which may be substitute with methyl group, ethyl group or propyl group; and aralkyl group such as benzyl group, phenethyl group or the like, which may be substitute with methyl group, ethyl group or propyl group.
In the general formula (10), R21 is a hydrogen atom or a group represented by the general formula (11), wherein R22, R23 and R24 independently represent hydroxy group, a straight-chain or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, preferably hydroxy group, or a straight-chain or branched alkyl or alkoxy group having 1 to 10 carbon atoms, and more preferably hydroxy group or a straight-chain or branched alkyl or alkoxy group having 1 to 6 carbon atoms.
Specific examples of R22, R23 and R24 independently include hydroxy group; alkyl group such as methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, or the like; alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group or the like; cycloalkyl group such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group or the like; aryl group such as phenyl group, naphthyl group, anthryl group, biphenyl group or the like, which may be substituted with methyl group, ethyl group, propyl group.; and aralkyl group such as benzyl group, phenethyl group and the like, which may be substituted with methyl group, ethyl group, propyl group.
In the general formula (10), the arylene group for Ar19 or Ar21 is independently an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene or naphthylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of the arylene group for Ar19 and Ar21 include phenylene group, naphthylene group, anthrylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In addition, Ar19 and Ar21 in the general formula (10) may be independently an aromatic amine group represented by the general formula (6) or an arylene ethenylene group represented by the general formula (7).
Examples of aryl group for Ar20 in the general formula (10) include an aryl group having 6 to 30 carbon atoms, preferably a phenyl group, naphthyl or anthrylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of aryl group for Ar20 include phenyl group, naphthyl group, anthryl group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In the general formula (10), Ar20 may be an aromatic amine group represented by the general formula (8), or an arylene ethenylene group represented by the general formula (9).
In the general formula (10), a ring may be formed between Ar19 and Ar20, Ar19 and Ar21, or Ar20 and Ar21.
In the general formula (12), R25, R26 and R27 independently represent a straight-chain or branched alkyl or alkoxy group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 30 carbon atoms or an aralkyl group having 7 to 32 carbon atoms, an arylene ethenylene group represented by the general formula (9), an aromatic amine group represented by the general formula (13), preferably a straight-chain or branched alkyl or alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an arylene ethenylene group represented by the general formula (9), or an aromatic amine group represented by the general formula (13), more preferably a straight-chain or branched alkyl or alkoxy group having 1 to 6 carbon atoms, an arylene ethenylene group represented by the general formula (9), or an aromatic amine group represented by the general formula (13).
Specific examples of R25, R26 and R27 include independently an alkyl group such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group, or the like; alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group or the like; cycloalkyl group such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexl group or the like; aryl group such as phenyl group, naphthyl group, anthryl group, biphenyl group or the like, which may be substitute with methyl group, ethyl group or propyl group; and aralkyl group such as benzyl group, phenethyl group or the like, which may be substitute with methyl group, ethyl group or propyl group.
In the general formula (13), the arylene group for Ar22 is an arylene group having 6 to 30 carbon atoms, preferably an arylene group having 6 to 20 carbon atoms, and more preferably a phenylene or naphthylene group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of the arylene group for Ar22 include phenylene group, naphthylene group, anthrylene group and the like, which may be substituted with methyl group, ethyl group or propyl group.
In addition, Ar22 in the general formula (13) may be an aromatic amine group represented by the general formula (6) or an arylene ethenylene group represented by the general formula (7).
In the general formula (13), the aryl group for Ar23 and Ar24 is an aryl group having 6 to 30 carbon atoms, preferably an aryl group having 6 to 20 carbon atoms, and more preferably a phenyl or biphenyl group which may be substituted with a straight-chain or branched alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 3 to 6 carbon atoms.
Specific examples of the aryl group for Ar23 and Ar24 include phenyl group, naphthyl group, anthryl group and the like, which may be substituted with methyl group, ethyl group or propyl group.
Ar23 and Ar24 in the general formula (13) are independently an aromatic amine group represented by the general formula (8) or an arylene ethenylene group represented by the general formula (9).
The third hole transporting polymer of the present invention is the second hole transporting polymer which contains at least one group represented by the above general formula (12) in an amount of from 10% by mole to 150% by mole based on the total silicon atoms belonging to said hole transporting polymer except silicon atoms contained in said group, and the content of the hydroxyl group is less than 10% by mole, preferably less than 5% by mole, more preferably less than 1% by mole, based on the total silicon atoms belonging to said hole transporting polymer except silicon atoms contained in said group.
The third hole transporting polymer of the present invention has been improved in durability.
Examples of the structural unit contained in the second hole transporting polymer or the third hole transporting polymer include the structural unit represented following formula (s1) and (s2). 
In the formula, A represents an aromatic amine group in the repeating structural unit represented by the general formula (5). B represents any one of R8 to R11 in the general formula (5), or the group represented by the general formula (12). 
In the formula, Axe2x80x2 represents an aromatic amine group in the repeating structural unit represented by the general formula (10). Bxe2x80x2 represents R19 or R20 in the general formula (10) or the group represented by the general formula (12).
The method of producing the first hole transporting polymer of the present invention is characterized by hydrolyzing and condensing at least one silane compound represented by the above general formula (14), and specific examples thereof include method of hydrolyzing and condensing in the presence or absence of a solvent under an acidic or basic condition.
A mixture obtained by mixing a silane compound represented by the above general formula (14) with one or more of a silane compound represented by the following general formula (23) may be hydrolyzed and condensed. 
wherein X represents a halogen atom or an alkoxy group having 1 to 6 carbon atoms; and Rxe2x80x3 represents an alkyl or aryl group having 1 to 12 carbon atoms, which may be the same or different.
As the hydrolysis condition, a basic condition is preferred. The base used to give the basic condition is not specifically limited, and inorganic and organic bases can be used. Among them, an organic base is particularly preferred. The solvent may be any one which can dissolve the above silane compounds, and is preferably an organic solvent having high polarity, such as ether solvent, amine solvent or the like. A mixed solvent of two or more kinds can also be used. The reaction temperature is usually in the range of from 0 to 150xc2x0 C., preferably from 40 to 100xc2x0 C. The reaction time, depending on a silane compound which is hydrolyzed and condensed, is normally from 30 minutes to 100 hours.
In the general formula (14), X is a halogen atom or a straight-chain or branched alkoxy group having 1 to 20 carbon atoms, preferably a halogen atom or a straight-chain or branched alkoxy group having 1 to 10 carbon atoms, and more preferably a halogen atom or a straight-chain or branched alkoxy group having 1 to 3 carbon atoms.
Specific examples of X include halogen atom such as iodine, bromine, chlorine, fluorine or the like; and alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group or the like.
Preferable group for R1, Ar1, Ar2 and Ar3 in the general formula (14) and specific examples thereof are the same as those for R1, Ar1, Ar2 and Ar3 in the general formula (1), and a ring may be formed between Ar1 and Ar2, Ar1 and Ar3, or Ar2 and Ar3.
The method of synthesizing the silane compound represented by the above general formula (14) is not specifically limited, and specific examples thereof include method of obtaining the silane compound by the methasesis reaction between an alkylhalosilane, alkylalkoxysilane or alkylhaloalkoxysilane compound, and a Grignard reagent or a lithium reagent of an organic compound.
The method of producing the second hole transporting polymer of the present invention is characterized by hydrolyzing and condensing at least one silane compound represented by the above general formula (15), or a mixture of at least one silane compound represented by the above general formula (15) and at least one silane compound represented by the above general formula (16), and specific examples thereof include method of hydrolyzing and condensing in the presence or absence of a solvent under an acidic or basic condition.
A silane compound represented by the general formula (15) or a mixture of a silane compound represented by the general formula (15) and a silane compound represented by the above general formula (16) may be hydrolyzed and condensed in the presence of a silane compound having an alkoxy group or a halogen atom, other than the above silane compound.
As the hydrolysis condition, a basic condition is preferred. The base used to give the basic condition is not specifically limited, and inorganic and organic bases can be used. Among them, an organic base is particularly preferred. Examples of an organic base include diethyl amine, triethyl amine, butylamine, dibutylamine, tributylamine and pyridine. The solvent may be any one which can dissolve the above silane compounds, and is preferably an organic solvent having high polarity, such as ether solvent, amine solvent or the like. A mixed solvent of two or more can also be used. The reaction temperature is usually in the range of from 0 to 150xc2x0 C., preferably from 40 to 100xc2x0 C. The reaction time, depending on a silane compound which is hydrolyzed and condensed, is usually from 30 minutes to 100 hours.
In the general formula (15), R30, R31, R32 and R33 are independently a halogen atom, a straight-chain or branched alkyl group or alkoxy group having 1-20 carbon atoms, a cycloalkyl group having 3-20 carbon atoms, an aryl group having 6-30 carbon atoms, or an aralkyl group having 7-32 carbon atoms, preferably a halogen atom, a straight-chain or branched alkyl group or alkoxy group having 1-10 carbon atoms or a cycloalkyl group having 3-10 carbon atoms, more preferably a halogen atom, a straight-chain or branched alkyl group or alkoxy group having 1-6 carbon atoms.
Specific examples of R30, R31, R32 and R33 independently include: a halogen atom such as iodine, bromine, chlorine and fluorine; an alkyl group such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, heptyl group, octyl group and the like; an alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group and the like; a cycloalkyl group such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group; an aryl group such as phenyl group, naphtyl group, anthryl group, biphenyl group which may be substituted with methyl group, ethyl group and propyl group; an aralkyl group such as benzyl group, phenetyl group and the like, which may be substituted with methyl group, ethyl group and propyl group.
In the general formula (15), R28 and R29 independently are a halogen atom or a straight-chain or branched alkoxy group having 1-20 carbon atoms, preferably a halogen atom, or a straight-chain or branched alkoxy group having 1-10 carbon atoms, more preferably a halogen atom, or a straight-chain or branched alkoxy group having 1-3 carbon atoms.
Specific examples of R28 and R29 independently include: a halogen atom such as iodine, bromine, chlorine and fluorine; an alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group and the like.
Preferable group for Ar25 and Ar27 in the general formula (15) and specific examples thereof are the same as those of Ar9 in the general formula (5) or as those of Ar19 in the general formula (10).
Preferable group for Ar25 and Ar27 in the general formula (15) and specific examples thereof are the same as those of Ar10 in the general formula (5). A ring may be formed between Ar25 and Ar26, between Ar25 and Ar27, or between Ar26 and Ar27.
In the general formula (16), R35 and R36 independently are a halogen atom, a straight-chain or branched alkyl group or alkoxy group having 1-20 carbon atoms, a cycloalkyl group having 3-20 carbon atoms, an aryl group having 6-30 carbon atoms, or an aralkyl group having 7-32 carbon atoms, preferably a halogen atom, a straight-chain or branched alkyl group or alkoxy group having 1-10 carbon atoms, or a cycloalkyl group having 3-10 carbon atoms, more preferably a halogen atom, a straight-chain or branched alkyl group or alkoxy group having 1-6 carbon atoms.
Specific example of R35 and R36 independently include: a halogen atom such as iodine, bromine, chlorine, fluorine; an alkyl group such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and the like; an alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group, and the like; a cycloalkyl group such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, and the like; an aryl group such as phenyl group, naphtyl group, anthryl group, biphenyl group, and the like, which may be substituted with methyl group, ethyl group, and propyl group; and an aralkyl group such as benzyl group, phenetyl group, and the like, which may be substituted with methyl group, ethyl group, and propyl group.
In the general formula (16), R34 is a halogen atom, or a straight-chain or branched alkoxy group having 1-20 carbon atoms, preferably a halogen atom or a straight-chain or branched alkoxy group having 1-10 carbon atoms, and more preferably a halogen atom, or a straight-chain or branched alkoxy group having 1-3 carbon atoms.
Specific examples of R34 include: a halogen atom such as iodine, bromine, chlorine, and fluorine; an alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group, and the like.
In the general formula (16), the arylene group for Ar28 is an arylene group having 6-30 carbon atoms, preferably an arylene group having 6-20 carbon atoms, and more preferably a phenylene group or a naphthylene group which may be substituted with a straight-chain or branched alkyl group having 1-6 carbon atoms or a cycloalkyl group having 3-6 carbon atoms.
Specific examples of the arylene group in Ar28 include a phenylene group, a naphthylene group, an anthrylene group, and the like, which may be substituted with methyl group, ethyl group, and propyl group.
In the general formula (16), Ar28 may be an arylene ethenylene group represented by the general formula (17).
In the general formula (17), Ar31 and Ar32 are independently an arylene group having 6-30 carbon atoms, preferably an arylene group having 6-20 carbon atoms, and more preferably a phenylene group which may be substituted with a straight-chain or branched alkyl group having 1-6 carbon atoms or a cycloalkyl group having 3-6 carbon atoms.
Specific examples of Ar31 and Ar32 independently include phenylene group, naphthylene group, anthrylene group, and the like, which may be substituted with methyl group, ethyl group, and propyl group.
In the general formula (17), R37 and R38 independently are hydrogen atom, a straight-chain or branched alkyl group having 1-20 carbon atoms, a cycloalkyl group having 3-20 carbon atoms, an aryl group having 6-30 carbon atoms, or an aralkyl group having 7-32 carbon atoms, preferably hydrogen atom, a straight-chain or branched alkyl group having 1-10 carbon atoms, a cycloalkyl group having 3-10 carbon atoms, an aryl group having 6-20 carbon atoms, or an aralkyl group having 7-22 carbon atoms, more preferably hydrogen atom, a straight-chain or branched alkyl group having 1-6 carbon atoms, phenyl group which may be substituted with a straight-chain or branched alkyl group having 1-6 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms.
Specific examples of R37 and R38 independently include hydrogen atom, methyl group, ethyl group, propyl group, and phenyl group which may be substituted with methyl group, ethyl group, and propyl group.
In the general formula (16), the aryl group for Ar29 and Ar30 independently is an aryl group having 6-30 carbon atoms, preferably an aryl group having 6-20 carbon atoms, more preferably a phenyl group or naphtyl group which may be substituted with a straight-chain or branched alkyl group having 1-6 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms.
Specific examples of the aryl group in Ar29 and Ar30 include independently, a phenyl group, naphtyl group, anthryl group, and the like, which may be substituted with methyl group, ethyl group, and propyl group.
Ar29 and Ar30 in the general formula (16) may be an aromatic amine group represented by the general formula (18).
In the general formula (18), Ar33 is an arylene group having 6-30 carbon atoms, preferably an arylene group having 6-20 carbon atoms, more preferably a phenylene group or a biphenylene group which may be substituted with a straight-chain or branched alkyl group having 1-6 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms.
Specific examples of Ar33 include phenylene group, naphthylene group, anthrylene group, biphenylene group, and the like, which may be substituted with methyl group, ethyl group, and propyl group.
R39 and R40 in the general formula (18) independently include a straight-chain or branched alkyl group having 1-20 carbon atoms, a cycloalkyl group having 3-20 carbon atoms, an aryl group having 6-30 carbon atoms, and an aralkyl group having 7-32 carbon atoms, preferably a straight-chain or branched alkyl group having 1-10 carbon atoms, a cycloalkyl group having 3-10 carbon atoms, an aryl group having 6-20 carbon atoms, and an aralkyl group having 7-22 carbon atoms, and more preferably a phenyl group or a naphtyl group which may be substituted with a straight-chain or branched alkyl group having 1-6 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms.
Specific examples of R39 and R40 independently include phenyl group, naphtyl group, anthryl group, biphenyl group, and the like, which may be substituted with methyl group, ethyl group, and propyl group.
In the general formula (18), a ring may be formed between Ar33 and R39, between Ar33 and R40, or between R39 and R40.
Ar29 and Ar30 in the general formula (16) may be an arylene ethenylene group represented by the general formula (19).
In the general formula (19), Ar34 is an arylene group having 6-30 carbon atoms, preferably an arylene group having 6-20 carbon atoms, more preferably a phenylene group which may be substituted with a straight-chain or branched alkyl group having 1-6 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms.
Specific examples of Ar34 include a phenylene group, a naphthylene group, an anthrylene group, and the like, which may be substituted with methyl group, ethyl group, and propyl group.
In the general formula (19), Ar34 is an aryl group having 6-30 carbon atoms, preferably an aryl group having 6-20 carbon atoms, more preferably a phenyl group which may be substituted with a straight-chain or branched alkyl group having 1-6 carbon atoms, or a cycloalkyl group having 3-6 carbon atoms.
Specific examples of Ar34 include a phenyl group, a naphtyl group, an anthryl group, and the like, which may be substituted with methyl group, ethyl group, and propyl group.
In the general formula (19), R41 and R42 independently include hydrogen atom, a straight-chain or branched alkyl group having and 1-20 carbon atoms, a cycloalkyl group having 3-20 carbon atoms, an aryl group having 6-30 carbon atoms, and an aralkyl group having 7-32 carbon atoms, preferably hydrogen atom, a straight-chain or branched alkyl group having and 1-10 carbon atoms, a cycloalkyl group having 3-10 carbon atoms, an aryl group having 6-20 carbon atoms, and an aralkyl group having 7-22 carbon atoms, more preferably hydrogen atom, a straight-chain or branched alkyl group having 1-6 carbon atoms, a phenyl group which may be substituted with a straight-chain or branched alkyl group having 1-6 carbon atoms or a cycloalkyl group having 3-6 carbon atoms.
Specific examples of R41 and R42 independently include hydrogen atom, methyl group, ethyl group, and propyl group, or a phenyl group which may be substituted with methyl group, ethyl group, and propyl group. In the general formula (16), a ring may be formed between Ar28 and Ar29, between Ar28 and Ar30, or between Ar29 and Ar30.
The method of synthesizing the silane compounds represented by the above general formula (15) and (16) are not specifically limited, and specific examples thereof include method of obtaining the silane compound by the methasesis reaction between an alkylhalosilane, alkylalkoxysilane or alkylhaloalkoxysilane compound, and a Grignard reagent or a lithium reagent of an organic compound.
The method of producing the second or the third hole transporting polymer of the present invention is characterized by that a silane compound represented by the general formula (20) is reacted with a hole transporting polymer manufactured by the above method of producing the second hole transporting polymer. Specific examples thereof include method of hydrolyzing and condensing in the presence or absence of a solvent under an acidic or basic condition.
As the hydrolysis condition, a basic condition is preferred. The base used to give the basic condition is not specifically limited, and inorganic and organic bases can be used. Among them, an organic base is particularly preferred. Examples of an organic base include diethyl amine, triethyl amine, butylamine, dibutylamine, tributylamine and pyridine. The solvent may be any one which can dissolve the above silane compounds, and is preferably an organic solvent having high polarity, such as ether solvent, amine solvent or the like. A mixed solvent of two or more can also be used.
The reaction temperature is usually in the range of 0 to 150xc2x0 C., preferably not lower than 20xc2x0 C. and not higher than 100xc2x0 C., and more preferably not lower than 40xc2x0 C. and not higher than 80xc2x0 C.
In the general formula (20), X is a halogen atom, hydroxyl group or a straight-chain or branched alkoxy group having 1-20 carbon atoms, preferably, a halogen atom, hydroxyl group and more preferably, a halogen atom.
Specific examples of X include: a halogen atom such as iodine, bromine, chlorine, and fluorine; an alkoxy group such as methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, a pentyloxy group, a hexyloxy group, a heptyloxy group, an octyloxy group, and the like.
Preferable group for R25, R26, and R27 in the general formula (20) and specific examples thereof include the same as those of R25, R26 and R27 in the general formula (12).
The method of synthesizing the silane compound represented by the above general formula (20) is not specifically limited, and specific examples thereof include method of obtaining the silane compound by the methasesis reaction between an alkylhalosilane, alkylalkoxysilane or alkylhaloalkoxysilane compound, and a Grignard reagent or a lithium reagent of an organic compound.
The organic EL device of the present invention will be described hereinafter.
The organic electroluminescence device of the present invention is characterized by [7] an organic electroluminescence device comprising a pair of electrodes of an anode and a cathode, at least one of which is transparent or semitransparent, and at least one layer of an organic material formed between the electrodes, wherein the organic material layer contains the first hole transporting polymer [1], the second hole transporting polymer [2] or the third hole transporting polymer [3].
The organic electroluminescence device of the present invention is characterized by [8] an organic electroluminescence device comprising a pair of electrodes of an anode and a cathode, at least one of which is transparent or semitransparent, and a light emitting layer formed between the electrodes, wherein the light emitting layer contains the first hole transporting polymer [1], the second hole transporting polymer [2], or the third hole transporting polymer [3].
The organic electroluminescence device of the present invention is characterized by [9] an organic electroluminescence device comprising a pair of electrodes of an anode and a cathode, at least one of which is transparent or semitransparent, and a light emitting layer formed between the electrodes, wherein a hole transporting layer containing the first hole transporting polymer [1], the second hole transporting polymer [2], or the third hole transporting polymer [3] is provided adjacent to the light emitting layer between the anode and the light emitting layer.
The organic electroluminescence device of the present invention is characterized by [10] the organic electroluminescence device described in the item [8] or [9], wherein an electron transporting layer containing an electron transporting material is provided adjacent the light emitting layer between the cathode and the light emitting layer.
The organic electroluminescence device of the present invention is characterized by [11] the organic electroluminescence device described in any one of the organic EL device, wherein the light emitting layer contains a light emitting polymer, which contains a repeating structural unit represented by the following general formula (24) in the proportion of 50% by mol based on the total repeating structural units and has a polystyrene-reduced number-average molecular weight of 103 to 107.
xe2x80x94Arxe2x80x94CRxe2x95x90CRxe2x80x2xe2x80x83xe2x80x83(24)
wherein Ar represents an arylene group or a heterocylic compound group having 4 to 20 carbon atoms which take part in a conjugated bond; and R and Rxe2x80x2 independently represent a group selected from the group consisting of hydrogen atom, alkyl group having 1 to 20 carbon atoms, aryl group having 6 to 20 carbon atoms, heterocyclic compound having 4 to 20 carbon atoms and cyano group.
The structure of the organic EL device of the present invention is not specifically limited, and may be any organic EL device having at least one organic layer between a pair of electrodes of an anode and a cathode, at least one of which is transparent or semitransparent, wherein the organic layer contains the above described hole transporting polymer. Preferred examples of the structure of the organic EL device of the present invention include those wherein a light emitting layer contains the hole transporting polymer, those obtained by layering a light emitting layer on a hole transporting layer containing the hole transporting polymer and providing a pair of electrodes on both surfaces and those obtained by layering an electron transporting layer containing an electron transporting material between a light emitting layer and a cathode. Single or multi-layer of the light emitting layer and charge transporting layer independently may be used.
The following charge transporting material, i.e. electron transporting material or hole transporting material may be contained in the hole transporting layer unless th e operation of the hole transporting polymer is inhibited. When the other hole transporting material is mixed with the hole transporting polymer, the amount is not more than 100% by weight, preferably not more than 40% by weight, and most preferably not more than 20% by weight, based on the hole transporting polymer. When the electron transporting material is mixed, the mixing ratio may be appropriately selected considering the luminous efficacy.
The above charge transporting material, which is used alone or in combination thereof in the organic EL device of the present invention, is not specifically limited, and known materials can be used. Examples of the hole transporting material include pyrazoline derivatives, arylamine derivatives, stilbene derivatives, triphenyldiamine derivatives and the like; and examples of the electron transporting material include oxadiazole derivatives, anthraquinodimethane and its derivatives, benzoquinone and its derivatives, naphthoquinone and its derivatives, anthraquinone and its derivatives, tetracyanoanthraquinondimethane and its derivatives, fluorenone derivatives, diphenyldicyanoethylene an d its derivatives, diphenoquinone derivatives, metal complex of 8-hydroxyquinoline and its derivatives and the like.
Specific examples thereof include those described in JP-A-63-70257, JP-A-63-175860, JP-A-2-135359, JP-A-2-135361, JP-A-2-209988, JP-A-3-37992 and JP-A-3-152184. Among them, the hole transporting material preferably includes triphenyldiamine derivatives and the electron transporting material preferably includes oxadiazole derivatives, benzoquinone and its derivatives, anthraquinone and its derivatives and metal complex of 8-hydroxyquinoline and its derivatives. More preferably, the hole transporting material includes 4,4xe2x80x2-bis(N(3-methylphenyl)-N-phenylamino)biphenyl and the electron transporting material includes 2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole, benzoquinone, anthraquinone and tris(8-quinolinol)aluminum.
Among them, the compound of the electron transporting material and/or the compound of the hole transporting material may be used. These electron transporting materials and hole transporting materials may be used alone or in combination thereof.
When the hole transporting layer is provided adjacent to the light emitting layer and the electron transporting layer is further provided adjacent to the light emitting layer between the light emitting layer and cathode, the electron transporting layer may be formed by using the above electron transporting material. When the second hole transporting layer is provided between the hole transporting layer and anode, the second hole transporting layer may be formed by using the above hole transporting material.
When the above described charge transporting material and light emitting material are used in combination, the amount of the charge transporting material used varies depending on the kind of the compound to be used. Therefore, the amount may be appropriately decided unless sufficient film forming property and light emitting characteristics are inhibited. The amount of the charge transporting material is normally from 1 to 4 0% by weight, and preferably from 2 to 30% by weight, based on the light emitting material.
The known light emitting material, which can be used in the light emitting layer of the organic EL device of the present invention, is not specifically limited. As the low molecular weight compound, for example, there can be used naphthalene derivatives, anthracene and its derivatives, perylene and its derivatives, polymethine dyes, xanthene dyes, coumarin dyes and cyanine dyes; and metal complex of 8-hydroquinoline and its derivatives, aromatic amine, tetraphenylcyclopentadiene and its derivatives, and tetraphenylbutadiene and its derivatives. Specific examples thereof include known light emitting materials such as those described in JP-A-57-51781 and JP-A-59-194393.
As the polymeric compound, for example, there can be used conjugated light emitting polymers such as poly(p-phenylene) and its derivatives, poly(p-phenylenevinylene) and its derivatives, polyfluorene and its derivatives, polyquinoline and its derivatives, polyquinoxaline and its derivatives and the like. Specific examples thereof include known light emitting polymers such as those described in JP-A-5-202355 and JP-A-5-320635, JP-A-7-97569, JP-A-7-147190, JP-A-7-278276 and JP-A-7-300580.
As the light emitting material contained in the light emitting layer of the organic EL device of the present invention, the light emitting polymer is preferred. Examples of the light emitting polymer include light emitting polymer as polyarylenevinylene and its derivatives, which contains the repeating unit represented by the above general formula (24) in the proportion of not less than 50% by mol based on the total repeating structural units and has a polystyrene-reduced number-average molecular weight of 103 to 107. Depending on the structure of the repeating unit, the proportion of the repeating unit represented by the above general formula (24) is preferably not less than 70% by mol based on the total repeating structural units. The light emitting polymer may contain a divalent aromatic compound group or its derivatives, a divalent heterocyclic compound or its derivatives, or a group obtained by using them in combination as the repeating unit represented by the above general formula (24). The repeating unit represented by the above general formula (24) may be bonded in a non-conjugated unit having an ether group, an ester group, an amide group, an imide group or the like. Alternatively, the non-conjugated portion may be contained in the repeating unit.
When a light emitting material is a light emitting polymer which contains the repeating unit of the general formula (24), Ar of the general formula (24) includes arylene or heterocyclic compound group having 4 to 20 carbon atoms which take part in the conjugated bond.
Examples of Ar are described in JP-10-46138, specifically. Among them, phenylene group, substituted phenylene group, biphenylene group, substituted biphenylene group, naphthalenediyl group, substituted naphthalenediyl group, anthracene-9,10-diyl group, substituted anthracene-9,10-diyl group, pyridine-2,5-diyl group, thienylene group or substituted thienylene group is preferable. More preferable groups are phenylene group, biphenylene group, naphthalenediyl group, pyridine-2,5-diyl and thienylene group.
When R and Rxe2x80x2 of the general formula (24) is a group other than hydrogen a cyano group, examples of R and Rxe2x80x2 include the alkyl group having 1 to 20 carbon atoms such as methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, decyl group, lauryl group and the like, preferably methyl group, ethyl group, pentyl group, hexyl group, heptyl group and octyl group.
Examples of R and Rxe2x80x2 include an aryl group such as phenyl group, 4-C1-12 alkoxyphenyl group (C1-12 shows 1 to 12 carbon atoms, the same rule applies correspondingly to the following), 4-C1-12alkylphenyl group, 1-naphthyl group, 2-naphthyl group and the like.
In view of the solvent solubility , Ar of the general formula (24) is preferably substituted with a group selected from the group consisting of alkyl, alkoxy or alkylthio group having 4 to 20 carbon atoms, aryl or aryloxy group having 6 to 18 carbon atoms, and heterocyclic compound group having 4 to 14 carbon atoms.
Examples of the substituent are as follows. Examples of the alkyl group having 4 to 20 carbon atoms include butyl group, pentyl group, hexyl group, heptyl group, octyl group, decyl group, lauryl group and the like, preferably pentyl group, hexyl group, heptyl group and octyl group.
Examples of the alkoxy group having 4 to 20 carbon atoms include butoxy group, pentyloxy group, hexyloxy group, heptyloxy group, octyloxy group, decyloxy group, lauryloxy group and the like, preferably pentyloxy group, hexyoxyl group, heptyloxy group and octyloxy group.
Examples of the alkylthio group include butylthio group, pentylthio group, hexylthio group, heptylthio group, octylthio group, decylthio group, laurylthio group and the like, preferably pentylthio group, hexylthio group, heptylthio group and octylthio group.
Examples of the aryl group include phenyl group, 4-C1-12 alkoxyphenyl group, 4-C1-12alkylphenyl group, 1-naphthyl group, 2-naphthyl group and the like.
Examples of the aryloxy group include phenoxy group. Examples of the heterocyclic compound group include 2-thienyl group, 2-pyrrolyl group, 2-furyl group, 2-, 3- or 4-pyridyl group and the like.
The number of these substituents varies depending on the molecular weight of the light emitting polymer and construction of the repeating unit. In order to obtain a light emitting polymer having high solubility, the number of these substituents is preferably at least one per molecular weight of 600.
The method of synthesizing the light emitting polymer is not specifically limited, and examples thereof include method described in JP-A-5-202355.
The light emitting polymer used in the organic EL device of the present invention may be a random block or graft copolymer, or a polymer having an intermediate construction of them, e.g. a random copolymer having block polymer tendency . In order to obtain a light emitting polymer having high quantum yield of fluorescence, the random copolymer having a block polymer tendency, or block or graft copolymer is better than the perfect random copolymer.
Since the organic EL device of the present invention utilizes light emission from a thin film, a light emitting polymer having luminescence at the solid state is used.
Examples of the good solvent to the light emitting polymer include chloroform, methylene chloride, dichloroethane, tetrahydrofuran, toluene, xylene and the like. The light emitting polymer can be normally dissolved in these solvents in an amount of not less than 0.1% by weight, although it varies depending on the structure or molecular weight of the light emitting polymer.
The polystyrene-reduced molecular weight of the light emitting polymer used in the organic EL device of the present invention is preferably within the range from 103 to 107, and the preferable polymerization degree depends on the repeated structure and it""s proportion. In view of the film forming property, the total number of the repeated structures is preferably within the range from 4 to 10000, more preferably from 5 to 3000, and particularly from 10 to 200.
When these light emitting polymers are used as the light emitting material of the organic EL device, since the purity exerts an influence on light emitting characteristics, the light emitting polymer is preferably purified by reprecipitation, separation by means of chromatography or the like, after synthesis.
Next, a typical method of fabricating the organic EL device of the present invention will be described. As the pair of transparent or semitransparent electrodes composed of the anode and cat ho de, for example, tho se obtained by forming a transparent or semitransparent electrode on a transparent substrate such as glass, transparent plastic or the like can be used.
As the material of the anode, for example, there can be used conductive metal oxide films, semitransparent metal thin films and t he like. Specifically films of indium-tin oxide (ITO), tin oxide, zinc oxide, Au, Pt, Ag, Cu and the like are used. Examples of the production method include vacuum deposition method, sputtering method, plating method and the like.
A hole transporting layer containing a hole transporting polymer of the present invention as a hole transporting material is formed on the anode. Example of the method of forming the hole transporting layer containing the hole transporting polymer of the present invention include method of applying a melt, a solution or a mixed solution of a hole transporting material containing the hole transporting polymer, using an coating method such as spin coating method, casting method, dipping method, bar coating method, roll coating method or the like.
A film thickness of the hole transporting layer is preferably within the range from 0.5 nm to 10 xcexcm, and more preferably from 1 nm to 1 xcexcm. In order to enhance the luminous efficacy by increasing the current density, the film thickness is preferably within the range from 10 to 800 nm.
Then, a light emitting layer containing a light emitting material is formed. Examples of the method of forming the light emitting layer include a coating method such as method of vacuum deposition in the powdered state of these materials, method of applying a melt, a solution or a mixed solution of these materials by a spin coating method, a casting method, a dipping method, a bar coating method or roll coating method or the like. In case of using the low molecular weight compound, the vacuum deposition method is preferred. In case of using the polymeric compound, the method of applying a solution or a mixed solution by a spin coating method, a casting method, a dipping method, a bar coating method or roll coating method is preferred.
A film thickness of the light emitting layer is preferably within the range from 0.5 nm to 10 xcexcm, and more preferably from 1 nm to 1 xcexcm. In order to enhance the luminous efficacy by increasing the current density, the film thickness is preferably within the range from 10 to 500 nm.
When a thin film of the hole transporting layer and/or that of light emitting layer are formed by the coating method, it is preferable to dry with heating at a temperature within the range from 30 to 300xc2x0 C., and preferably from 60 to 200xc2x0 C., under reduced pressure or an inert atmosphere so as to remove the solvent after formation of the hole transporting layer and/or light emitting layer.
When an electron transporting layer is further layered on the light emitting layer, it is preferable to form the electron transporting layer after the light emitting layer was formed by the above-described film forming method.
The method of forming the film of the electron transporting layer is not specifically limited, and there can be used vacuum deposition method in the powder state; coating method such as spin coating method, casting method, dipping method, bar coating method, roll coating method, etc. after dissolving in the solution; or coating method such as spin coating method, casting method, dipping method, bar coating method, roll coating method, etc. after mixing a binder resin with an electron transporting material in the solution or molten state.
A binder resin to be mixed is not specifically limited, but those which do not inhibit electron transport are preferable. Those whose absorption to visible light is not strong are preferably used.
Examples thereof include poly(N-vinylcarbazole) and its derivatives, polyaniline and its derivatives, polythiophene and its derivatives, poly(p-phenylenevinylene) and its derivatives, poly(2,5-thienylenevinylene) and its derivatives, polycarbonate, polyacrylate, polymethyl acrylate, polymethyl methacrylate, polystyrene, polyvinyl chloride, polysiloxane and the like. It is preferable to use the coating method when using the polymeric compound because a film can be easily formed.
A film thickness of the electron transporting layer must be a thickness so that no pin hole is formed. When the film thickness is too large, the resistance of the device increase to require high driving voltage, unfavorably. Accordingly, the film thickness of the electron transporting layer is preferably within the range from 0.5 nm to 10 xcexcm, more preferably from 1 to 1 xcexcm, and particularly from 5 to 200 nm.
Then, an electrode is formed on the light emitting layer or the electron transporting layer. This electrode serves as an electron injection cathode. The material is not specifically limited, but a material having small work function is preferable. For example, there can be used Al, In, Mg, Ca, Li, Mgxe2x80x94Ag alloy, Inxe2x80x94Ag alloy, Mgxe2x80x94In alloy, Mgxe2x80x94Al alloy, Mgxe2x80x94Li alloy, Alxe2x80x94Li alloy, graphite thin film and the like. As the method of producing the cathode, there can be used vacuum deposition method, sputtering method and the like.